Beginning with the earliest commercialization of surfboards, various attempts have been made to provide an additional source of thrust to the surfboard or surfer beyond the surfer's own hands and arms. Most surfboards become stable enough to ride in the standing or crouched position (as opposed to prone or kneeling) once they reach planing speeds. Planing speeds are achieved when the surfboard exceeds the “hull speed” established by a bow wave as related to the length and displacement of the craft. The bow wave itself is a sort of speed barrier for any watercraft, where the bow wave acts as a “hill” requiring significant thrust to overcome. Meanwhile, the minimum speed of a rideable wave is around 5 m/s or 10 mph, which exceeds the maximum non-planing hull speed for a surfboard less than ˜3 m in length. Therefore, planing speeds are required to catch most waves on most boards.
To achieve planing speeds, break free of the surfboard's bow wave, and “catch” a wave, additional acceleration is required by the surfer. This acceleration is normally acquired by sliding down the face of a wave using gravity. Typically, only breaking or near-breaking waves offer sufficient downward angle and height for the surfer to achieve sufficient acceleration down the wave face to exceed hull speed of the board and begin planing. On small (slow) waves and large boards with greater hull speeds, catching a wave and achieving planing speeds can be relatively easy for a beginning surfer. However, it may be difficult for the surfer to position himself at the correct location in the breaking or near-breaking wave to achieve sufficient acceleration in waves much over 1 m. To both navigate to the right location and to provide the initial thrust necessary to enter the wave itself, the surfer must use his own muscle power. Further, there are a limited number of “breaks” at a given surfing location where the downward slope of the wave is sufficient to catch the wave. As wave height, and therefore speed, increase, the acceleration required to catch the wave also increases, further decreasing the size of suitable breaks. The result is often over-crowding at the best breaks, and an extreme physical effort required to position oneself at the best break and catch the wave. Only a limited number of waves typically break correctly, leading to most time spent by the surfer simply waiting for the right wave. Indeed, most time spent by a surfer is paddling and waiting, relatively little is spent riding the board.
If planing speeds could be achieved more easily, for example, on waves that were not yet breaking (less steep), there would be more waves at a given surfing location appropriate for surfing. Further, surfing fatigue associated with positioning and entering a wave could be reduced, thereby extending the time allowed for surfing. Also, less waiting would be required, making each surf session more enjoyable. Therefore, a means to increase thrust beyond maximum human power for surfboards and other wave-riding aquatic craft is desirable.
Previous attempts to add thrust beyond human power to a surfboard are largely focused around adding all of the required elements, including: 1) propeller or jet drive 2) motor, 3) energy storage, 4) motor control/switching system, and 5) user interface, to the surfboard body itself, thus resulting in a specialized surfboard, such as described in U.S. Pat. Nos. 6,142,840 and 3,324,822. There have also been attempts to modify a surfboard fin to include the required elements 1-4 above, in which the user interface is a remote control, and the surfboard is not therefore modified other than the fin itself, such as in U.S. patent publication 2003/0167991). In addition, there are a few designs in which the elements are separated, for example, where the energy storage and switching are attached to the surfboard and connected to a specialized surfboard thruster containing the propeller and motor.
Combinations of the various elements required to add thrust to a wave-riding craft suffer from a range of problems, making current designs impractical and unattractive to the average surfer. Firstly, a motorized board (the predominant type) is impractical for wave surfing for the following reasons. Surfers prefer changing board types for given wave conditions. While a motorized board could provide more ability for a fixed board type to work in different conditions, the average surfer is not likely to settle with just one board type. Also, when travelling to a surfing destination, the surfer may not prefer to bring the entire board. Secondly, every surfboard is designed to be represent some ideal combination of lightness (minimum displacement), strength, cost and shape. Adding motor, batteries and electronics to the board increases displacement, decreases board structural strength, increases cost and restricts possible shapes—all negative factors for the surfer. In particular, enclosing the electronics and batteries, or engine and fuel from the marine environment is very difficult and should it fail, the entire board is ruined. Boards can also break against reefs or beaches, and a large investment in a motorized board could easily be totally ruined in this manner as well. In most cases, motorized surfboards are best suited for use outside the breaking wave area.
One solution to the problems associated with the motorized surfboard is to place all or nearly all required elements into the fin, or another submerged thruster, which can then be detached from the board. This allows the surfer to provide additional motive thrust to any board he chooses. Unfortunately, the surfboard fin is typically far too small to contain all required elements, especially sufficient energy storage in the case of batteries. Any battery capable of fitting inside a surfboard fin today can only offer very little ride time. While devices exist where the power supply is external to the detachable thruster, such battery packs are bulky and located on the surfboard deck in a hard case, which will affect surfboard ride and utility. Further, while the surfer is paddling in the prone position, a hard case battery storage located anywhere on the surfboard deck will interfere with paddling and surfer comfort. This approach is limited to, for example, stand-up-paddleboards or kayaks where the user is not prone on the deck at any time.
While external power supply is preferred, any such external power supply should minimally interfere with the surfing activity. In accordance with aspects of various embodiments of the invention as described below, a power supply if worn by a user should conform to the contours of the user's body at the points of contact, preferably in a manner similar to a wetsuit, neoprene ankle strap, watch band, or padding of a camping backpack. If the power supply is attached to a board, it would preferably offer the lowest profile and displacement possible by matching the complex contours of the board's surface, which vary from board to board; in a similar manner to, for example, a sticker applied to a car windshield or foam rubber traction pads adhered to surfboards. In either the user-worn or board-attached cases, fundamentally rigid elements (batteries and electronics modules) must conform to the contours of the user or board. This conformance must take place through repeated attachment and detachment cycles. Further, such a power supply should be inherently waterproof and preferably sufficiently buoyant to remain floating if it becomes accidentally detached. Such a power supply should be easily and securely attached and detached from either the user or the board, for example using hook-and-loop straps, adhesives or suction cups.
As described earlier, a motorized thruster is only required to provide additional thrust during the initial phase of positioning and catching the wave. After this point, the motor is largely unnecessary and board performance is all-important. A motorized surfboard containing all required elements will inevitably sacrifice wave-riding performance due to increased weight when the motor is not operating (most of the riding time). And any surfboard design in which the propeller is located external to the board itself (e.g. not an inboard jet) will cause significant drag whilst not operating which will seriously negatively affect riding performance.
Surfing is a near-shore sport and shorelines accumulate free floating aquatic weeds and debris. These can easily foul a non-operating propeller or jet intake on an operating jet and utterly ruin the performance of both the surfboard and the motorized thruster.
The ideal system for adding thrust to a surfboard or other wave-riding craft would therefore offer a boost to the surfer when needed and essentially disappear when not needed, would conform to the contours of the board or user, and would also be easily detached and re-attached to any surfboard or wave-riding craft.